The present invention relates to shampoo compositions, and more particularly to shampoo compositions containing non-volatile silicone materials which condition the hair leaving it softer and more manageable.
When washing the hair with conventional shampoo compositions, the natural oils are removed together with the dirt and unwanted oils. When too much of the natural oil is removed, for example by especially frequent washing, the hair becomes less easy to comb or style, and subject to static build-up causing "flyaway."
Hair conditioners have been developed to try to restore the condition of the hair. These compositions are normally applied to hair after shampooing, left on the hair for a period of time and rinsed off. This process is time consuming and expensive since two separate products are needed.
During the mid-to-late 1980's, 2-in-1 conditioning shampoos have risen in popularity due to their convenience. Many brands now carry a conditioning version as part of their line. Conditioning shampoos present challenges to the formulator. Incorporating such conditioning agents as quaternary ammonium compounds, synthetic cationic polymers, and silicones into shampoo bases can be difficult. Also, deriving benefits from these conditioning agents when formulated into a shampoo base is troublesome.
Quaternary ammonium compounds are often incompatible with anionic shampoo ingredients. Even when they are successfully incorporated into a shampoo, their effectiveness is questioned. Synthetic cationic polymers have been used in anionic shampoo systems with some success, yet many tend to build up on the hair after repeated applications, and these materials' primary effect is directed more toward increasing manageability rather than wet and dry combing smoothness which is looked for in the standard 2-in-1 shampoo. Other conditioning shampoos employ such water soluble silicone materials as dimethicone copolyols yet they are believed to be less effective than insoluble silicones. The higher molecular weight insoluble, nonvolatile silicones are difficult to handle and most difficult to incorporate into a shampoo yet give optimum results on wet and dry hair.
Some conditioning 2-in-1 shampoo formulas have been developed which use a dispersion technique (see U.S. Pat. Nos. 4,704,272, 4,728,457, 4,788,272, and 5,085,857) to keep the insoluble, nonvolatile silicone from separating out of the shampoo. The practice of these patents in a number of popular shampoos employs Xanthan Gum to disperse the silicone. The problem with these types of shampoos is they present significant challenges to the skilled formulator.
It is generally believed in the industry that insoluble, nonvolatile silicones can not be emulsified directly into shampoo composition due to the generally high HLB value of anionic and amphoteric shampoo compositions and low required HLB of such silicones. (HLB stands for `Hydrophile-Lipophile Balance` and is a measure of the relative proportions of water-soluble and oil soluble components in a surfactant; see Griffin, W. C., J. Soc. Cosmetic Chemists 1949, 1311 and "Emulsions: Theory and Practice," p. 232 ff (P. Becher, Reinhold, 1965). For any given surfactant function, such as detergency, emulsification or wetting, there is usually an optimum HLB value.) Current emulsion technology dictates that the surfactants' HLB in a system must match the HLB requirement of the insoluble materials (i.e. silicone).
Nonionic surfactant based shampoos, without anionic or amphoteric surfactants, enable incorporation of higher levels of cationic materials and are able to be blended to the low HLB requirements of an insoluble, nonvolatile silicone. However, these systems are not favored because of the low foaming and high sebum stripping effects associated with predominantly nonionic detergent systems.
Non-volatile silicone oils are useful as conditioning agents, but again excessive amounts of silicone can dull the hair, and build-up of silicone on the hair can give a greasy appearance. Furthermore, the incorporation of silicone oil generally gives an antifoam effect.
We have found that the combination of an aqueous emulsion of a silicone oil conditioner in a surfactant-based composition will impart improved conditioning benefit to the hair with none of the undesirable dulling effects or greasy build-up seen with other conditioning products, and without the need for a two-step washing and conditioning procedure.
Accordingly, the invention provides an aqueous composition comprising, in addition to water, a mixture of emulsifiers, a insoluble, non-volatile silicone and a mixture of detergent surfactants.
A still further aspect, this invention provides a stable shampoo composition comprising a insoluble, non-volatile silicone without the presence of a Xanthan gum.
In addition, this invention provides a stable composition comprising an emulsified insoluble, non-volatile silicone having an HLB value greater than the HLB requirement specified for such silicone.
This invention also provides a method of making a stable composition comprising an emulsion of insoluble, non-volatile silicone in a aqueous solution having a much higher HLB value than theoretically specified for such silicone whereby the silicone is emulsified in an aqueous solution at the specified HLB value for such silicone. Then detergent surfactants are added tending to increase the HLB level while the silicone remains emulsified.